Americans have commemorated the 15th anniversary of the September 11, 2001, attacks on the United States that left nearly 3,000 people dead.

Ceremonies were being held on Sunday across the country to remember the victims, including the recital of the names of the dead, tolling church bells and a tribute at the site where New York City’s twin towers tumbled.

The names of the victims will also be read slowly by relatives during a ceremony at the 9/11 Memorial plaza in Lower Manhattan.

US President Barack Obama said Saturday the attack had been one of the darkest days in the history of the country.

The 9/11 attacks killed 2,983 people and caused about $10 billion worth of property and infrastructure damage.

US officials assert that the attacks were carried out by al-Qaeda terrorists but many experts have raised questions about the official account.

They believe that rogue elements within the US government orchestrated or at least encouraged the 9/11 attacks in order to accelerate the US war machine and advance the Zionist agenda.

This year’s 9/11 memorial comes just days after the US Congress passed a controversial legislation that allows relatives of the victims to sue Saudi Arabia for compensation.

Saudi Arabia has strongly opposed the legislation. It has threatened to sell off $750 billion in American assets if it becomes law.

Ties between Saudi officials and terrorists behind the 9/11 attacks were exposed when US lawmakers released 28 secret pages of a congressional investigation.

Several suspicious connections were outlined in the report between the 19 hijackers, 15 of whom were Saudi citizens, and the monarchy’s officials, though no definitive comment were made about the Saudi involvement.